Fix MAUI NuGet config pinning when workload feeds fall back

[matouskozak]

Summary

Share manifest resolution and feed fallback between commit discovery and workload installation. Read package metadata from the selected feed and reuse the resolved manifests during installation.

After dotnet12 was added, commit discovery found no mobile manifests there and used branch-HEAD NuGet configs. Installation separately fell back to dotnet11, so the configs were no longer pinned to the selected package versions.

Use the working-directory NuGet.config for both initial and fallback feed selection, including staged payloads. Pass this path through commit discovery and use the same config finder for uncached installation.

Validation

Internal build 3068838 passed with one Android CoreCLR Release configuration on Pixel8 and one iOS CoreCLR Release configuration on iPhone17 (onlySanityCheck=true).

Internal build 3068905 passed after the config-path correction, with the same two configurations. Both preparation and Helix passed. Logs confirm staged config selection, dotnet11 fallback, three pinned source commits, cached manifest reuse, and successful workload installation.

Temporary local regression checks also passed with different repository and staged config feed lists. No test files or temporary pipeline changes remain in the PR diff.

[Copilot]

🟡 Changes recommended

Fallback feed selection in _resolve_manifest_package is tied to the repo-root NuGet.config and can diverge from the NuGet.config discovered/used in CorrelationStaging scenarios, risking incorrect fallback behavior.

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Pull request overview

This PR centralizes MAUI workload manifest package resolution (including feed fallback) so commit discovery and workload installation use the same resolved manifest packages and their corresponding feed metadata, preventing NuGet.config pinning mismatches when the latest workload feed lacks mobile manifests.

Changes:

• Introduced _resolve_manifest_package to resolve the latest manifest package with a fallback feed and return the feed used.
• Updated _discover_repo_commits to reuse _resolve_manifest_package and cache per-feed NuGet flat container bases.
• Updated install_latest_maui to reuse _resolve_manifest_package (and cached results from commit discovery) instead of duplicating fallback logic.

File summaries

File	Description
src/scenarios/shared/mauisharedpython.py	Unifies manifest/feed resolution between commit discovery and workload install to keep workload package selection and NuGet.config pinning consistent across feed fallback.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 1
• Review effort level: Lite

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[Copilot]

🟢 Approval recommended

The change aligns feed fallback and manifest resolution across discovery/install as intended, with only a minor logging clarity nit noted.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 1
• Review effort level: Lite

[LoopedBard3]

This looks good.